题目

When ________ leave for Beijing? A. do you think he will               B. do you think will he C. you think he will                 D. do you think 答案：A 半径为1的球面上有A、B、C、D四点，且满足： ，则S△ABC＋S△ACD＋S△ADB的最大值(S为三角形的面积)为________．